The present invention relates to the removal of contaminants from fluid columns.
Most common methods of managing polluted fluid columns rely on sorbent devices comprised of non-woven fabric materials, such as polypropylene, or filtration systems utilizing activated carbon to remove contaminants from feed streams. In many instances, these methods of dealing with pollutants merely result in contaminants being transferred to a different location where they must once again be processed for disposal.
Use of sorbent devices is messy, labor intensive and time consuming. The transportation and proper disposal of non-woven textile sorbent devices containing contaminants present additional problems. In many instances, non-woven textile devices saturated with pollutants may be placed in a landfill where only a small amount of pressure can release contaminants from the sorbent devices. The free release of pollutants into a landfill facility accomplishes little more than converting fluid borne contaminants into land contaminants, making this option an ineffective means of dealing with polluted feed streams.
When utilizing activated carbon, contaminants in a feed stream coat the surface of the carbon with a glaze of the pollutants, reducing the sorptive capacity and the effectiveness of the carbon. This requires the carbon filtration media to be frequently replaced, increasing costs associated with extracting contaminants from the feed stream and generating a large volume of contaminated filtration media for processing and disposal. These prior art methods of dealing with contaminants in fluid columns are harmful to the environment in that the issue of proper disposal of free flowing contaminants remains.
Certain elastomer polymers have the capability of imbibing and solidifying contaminants. However, simply placing a bed of the polymer within a filtering container may result in a variety of deficiencies when attempting to utilize the polymer as a filtration media.
In U.S. Pat. No. 4,534,865, Sundberg teaches that when utilizing a cross-linked organic polymer as a filtration media, the flow of a feed stream through an absorption bed of polymer will be decreased, and ultimately terminated, by the swelling of the polymer material as it absorbs and retains contaminants passing through a container of cross-linked polymer.
Further, passing a feed stream through a container packed with solidifying polymer often results in an undesired channeling within the bed of polymer, especially at high flow rates and elevated operating pressures. As a feed stream forms irregular channels through a packed bed of polymer, tube-like passages comprised of a non-permeable, rubber-like material may form along the internal periphery of these channels as contaminants in the feed stream are imbibed and solidified by the polymer. High levels of contaminants may be discharged from a filtering container when a feed stream is encapsulated within the tube-like passages and segregated from that portion of the solidifying polymer still having a capacity for contaminant uptake.
Packaging the polymer material in an envelope of a non-woven textile material and randomly placing the polymer-filled devices within a filtering container may present similar problems of surface blockage and channeling. The problem of surface blockage may manifest itself once again as a layer of solidified contaminants may form just beneath the envelope of textile material that defines the overall shape of the device, sealing a significant amount of the polymer still having a capacity for contaminant uptake inside a layer of solidified contaminants.
Random placement of individual polymer-filled bags within a filtering container may further result in restricted flow and channeling due to the polymer-filled devices exhibiting an effect similar to that created by the use of sandbags as flood control devices. Loose polymer within a textile material envelope may shift and settle into cavities between surrounding polymer-filled devices, restricting the flow of the feed stream through the filtering container.
Further, as a feed stream passes through a filtering container packed with randomly placed polymer-filled bags, it may channel through only a portion of the container. Polymer-filled bags adjacent to these channels may absorb and solidify contaminants, then form solidified channels similar to the tube-like passages within a packed bed of solidifying polymer.